What table has the queued Workflow Events? This:
You can probably tweak the config settings of the workflow service.
If you go to your HEAT installation folder you'll see a WorfklowService folder.
In that folder is a WorkflowService.exe.config file where you can change the polling values.
I don't know exactly what each setting does and this can also affect performance on the application server, so you'll have to test this out.